DHT Heater using VCCS - PCB or Kit (Possible Group buy)
#16
Hi Andrew,
Put me down for 6 please.
Thanks,
James
Put me down for 6 please.
Thanks,
James
#17
Ok chaps, this is the rough and ready prototype measurement attempt #1.
I will repeat this as all good 'metrologists' should.
The scale is 200mV.
The 50hz is set as the fundamental, that's over 81db down so 17uV (perhaps a bit lower if you look at the graph) you need to add in the THD+N - that is -72dbFS that's all the stuff that isn't 50Hz) that's 44uV, so all in all a safe bet to say (assuming I am correct) we're at less than 200uV total niose, my other true RMS AC meter reckons its about 180uV noise with a 30khz low pass filter this is pretty much down in the noise floor of this meter as it reads 160uV with a shroted input.
I'll have a think about my measurement strategy and repeat later.
Andrew
I will repeat this as all good 'metrologists' should.
The scale is 200mV.
The 50hz is set as the fundamental, that's over 81db down so 17uV (perhaps a bit lower if you look at the graph) you need to add in the THD+N - that is -72dbFS that's all the stuff that isn't 50Hz) that's 44uV, so all in all a safe bet to say (assuming I am correct) we're at less than 200uV total niose, my other true RMS AC meter reckons its about 180uV noise with a 30khz low pass filter this is pretty much down in the noise floor of this meter as it reads 160uV with a shroted input.
I'll have a think about my measurement strategy and repeat later.
Andrew
Analogue, the lost world that lies between 0 and 1.
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#18
OK, so 200mV at 0db, that looks very nice - Something down in the 10's of uV is where we want to be !
So I see this is 5V AC in, what's the DC-out on this one ?
So I see this is 5V AC in, what's the DC-out on this one ?
"Once you find out ... the Circumstances ; then you can go out"
#20
OK, I grounded everything at the other end next to the meter and I get <110uV total AC noise on the output of the reg. Meter just grounded is 30uV, so this appears genuine.
Andrew
Andrew
Analogue, the lost world that lies between 0 and 1.
#21
Gratuitous breadboard shot - including clip leads.....phwaoor
Sounds OK, actually, more than OK, at least as good as the bench PSU, perhaps slightly more bass, if anything and more 'air'. So no worse, and perhaps slightly better. And I still have a working pair of 300B phew!
I need two of 'em now.
Sounds OK, actually, more than OK, at least as good as the bench PSU, perhaps slightly more bass, if anything and more 'air'. So no worse, and perhaps slightly better. And I still have a working pair of 300B phew!
I need two of 'em now.
Analogue, the lost world that lies between 0 and 1.
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#22
Nice work !
Ok, do you have a more accurate idea ( from Sim or hardware ) what the minimum AC-in would be to give a clean 5V out ...
( Same sort of question as per the IHT supplies we have ) .
Ok, do you have a more accurate idea ( from Sim or hardware ) what the minimum AC-in would be to give a clean 5V out ...
( Same sort of question as per the IHT supplies we have ) .
"Once you find out ... the Circumstances ; then you can go out"
#23
Very minimum AC in for 5v DC out is something like 7.5v-8.0v AC RMS, you won't get away with 6.3v, sorry, not enough headroom to regulate.
Here's the full breadboard shot.
Andrew
Here's the full breadboard shot.
Andrew
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#24
OK, I'll use my Guido ones for 300B's thenAndrew wrote:Very minimum AC in for 5v DC out is something like 7.5v-8.0v AC RMS, you won't get away with 6.3v, sorry, not enough headroom to regulate.
Andrew
But that suggests I could probably run 4P1L's (at 4.2V) from a 6V toroid , which usually give about 7V around here, if not loaded too hard. Sounds good.
"Once you find out ... the Circumstances ; then you can go out"
#26
Hi Andrew,
I would be interested in 2, maybe 4. If you want something commercial to compare with I could send you a couple of diyhifsupply modules I have spare. I believe they aren't as good as the Rod Coleman circuit in terms of sound.
Cheers,
Clive
I would be interested in 2, maybe 4. If you want something commercial to compare with I could send you a couple of diyhifsupply modules I have spare. I believe they aren't as good as the Rod Coleman circuit in terms of sound.
Cheers,
Clive
#27
Thanks Clive.
Ok so I had a module running all day and it doesn't seem to get hot, so that's a good start. I hope the final dsign will rn as cool. I still want to see if there's any value in getting the noise spectrum a bit cleaner, without chucking too much voltage and extra heat at it.
Andrew
Ok so I had a module running all day and it doesn't seem to get hot, so that's a good start. I hope the final dsign will rn as cool. I still want to see if there's any value in getting the noise spectrum a bit cleaner, without chucking too much voltage and extra heat at it.
Andrew
Analogue, the lost world that lies between 0 and 1.
#28
Hi Andrew, I'm interested to know your view on how your heater circuit would compare with Rob Coleman's it terms of performance. I seem to recall he goes on about feedback used in most other modules and how this effects DHTs. I'm looking for better heaters for my 2A3 preamp than the diyhifisupply ones. Rod's are a bit of a bitch to fit as thery need a separate ps board.
#29
I've not heard Rod's modules, not even studied his circuit - this is deliberate.Hi Andrew, I'm interested to know your view on how your heater circuit would compare with Rob Coleman's it terms of performance. I seem to recall he goes on about feedback used in most other modules and how this effects DHTs.
I'm using a "current source" so there should be no feedback into the signal on the cathode.
I'm trying really hard to get this all onto a single PCB at is ~50mmx80mm; it may need to be a bit bigger. I get a few extra db noise reduction in simulations (recall its pretty low at the moment) by smoothing the 'B+' a bit more before it hits the main regulator. What I need to find out is a) does this make a measureable difference, b) does this make an audible difference. That's my next job.
I'm looking for better heaters for my 2A3 preamp than the diyhifisupply ones. Rod's are a bit of a bitch to fit as thery need a separate ps board.
cheers,
Andrew
Analogue, the lost world that lies between 0 and 1.
#30
Sounds great, I read up on the link you gave, it sounds like the circuit should be as good as it gets.Andrew wrote:
I've not heard Rod's modules, not even studied his circuit - this is deliberate.
I'm using a "current source" so there should be no feedback into the signal on the cathode.
50 x 80 would be ideal as this is the same size as my current heaters. I could even suggest where the mounting holes go.....